Re: [RFC PATCH v2 1/4] mm/page_alloc: use helper functions to add/remove a page to/from buddy

[Aaron Lu]

On Tue, Mar 20, 2018 at 12:35:46PM +0100, Vlastimil Babka wrote:
> On 03/20/2018 09:54 AM, Aaron Lu wrote:
> > There are multiple places that add/remove a page into/from buddy,
> > introduce helper functions for them.
> > 
> > This also makes it easier to add code when a page is added/removed
> > to/from buddy.
> > 
> > Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
> > ---
> >  mm/page_alloc.c | 65 ++++++++++++++++++++++++++++++++++-----------------------
> >  1 file changed, 39 insertions(+), 26 deletions(-)
> > 
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 3db9cfb2265b..3cdf1e10d412 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -736,12 +736,41 @@ static inline void set_page_order(struct page *page, unsigned int order)
> >  	__SetPageBuddy(page);
> >  }
> >  
> > +static inline void add_to_buddy_common(struct page *page, struct zone *zone,
> > +					unsigned int order, int mt)
> > +{
> > +	set_page_order(page, order);
> > +	zone->free_area[order].nr_free++;
> 
> The 'mt' parameter seems unused here. Otherwise

An right, forgot to remove it...

> 
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

Thanks!

> 
> > +}
> > +
> > +static inline void add_to_buddy_head(struct page *page, struct zone *zone,
> > +					unsigned int order, int mt)
> > +{
> > +	add_to_buddy_common(page, zone, order, mt);
> > +	list_add(&page->lru, &zone->free_area[order].free_list[mt]);
> > +}
> > +
> > +static inline void add_to_buddy_tail(struct page *page, struct zone *zone,
> > +					unsigned int order, int mt)
> > +{
> > +	add_to_buddy_common(page, zone, order, mt);
> > +	list_add_tail(&page->lru, &zone->free_area[order].free_list[mt]);
> > +}
> > +
> >  static inline void rmv_page_order(struct page *page)
> >  {
> >  	__ClearPageBuddy(page);
> >  	set_page_private(page, 0);
> >  }
> >  
> > +static inline void remove_from_buddy(struct page *page, struct zone *zone,
> > +					unsigned int order)
> > +{
> > +	list_del(&page->lru);
> > +	zone->free_area[order].nr_free--;
> > +	rmv_page_order(page);
> > +}
> > +
> >  /*
> >   * This function checks whether a page is free && is the buddy
> >   * we can do coalesce a page and its buddy if
> > @@ -845,13 +874,10 @@ static inline void __free_one_page(struct page *page,
> >  		 * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
> >  		 * merge with it and move up one order.
> >  		 */
> > -		if (page_is_guard(buddy)) {
> > +		if (page_is_guard(buddy))
> >  			clear_page_guard(zone, buddy, order, migratetype);
> > -		} else {
> > -			list_del(&buddy->lru);
> > -			zone->free_area[order].nr_free--;
> > -			rmv_page_order(buddy);
> > -		}
> > +		else
> > +			remove_from_buddy(buddy, zone, order);
> >  		combined_pfn = buddy_pfn & pfn;
> >  		page = page + (combined_pfn - pfn);
> >  		pfn = combined_pfn;
> > @@ -883,8 +909,6 @@ static inline void __free_one_page(struct page *page,
> >  	}
> >  
> >  done_merging:
> > -	set_page_order(page, order);
> > -
> >  	/*
> >  	 * If this is not the largest possible page, check if the buddy
> >  	 * of the next-highest order is free. If it is, it's possible
> > @@ -901,15 +925,12 @@ static inline void __free_one_page(struct page *page,
> >  		higher_buddy = higher_page + (buddy_pfn - combined_pfn);
> >  		if (pfn_valid_within(buddy_pfn) &&
> >  		    page_is_buddy(higher_page, higher_buddy, order + 1)) {
> > -			list_add_tail(&page->lru,
> > -				&zone->free_area[order].free_list[migratetype]);
> > -			goto out;
> > +			add_to_buddy_tail(page, zone, order, migratetype);
> > +			return;
> >  		}
> >  	}
> >  
> > -	list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
> > -out:
> > -	zone->free_area[order].nr_free++;
> > +	add_to_buddy_head(page, zone, order, migratetype);
> >  }
> >  
> >  /*
> > @@ -1731,9 +1752,7 @@ static inline void expand(struct zone *zone, struct page *page,
> >  		if (set_page_guard(zone, &page[size], high, migratetype))
> >  			continue;
> >  
> > -		list_add(&page[size].lru, &area->free_list[migratetype]);
> > -		area->nr_free++;
> > -		set_page_order(&page[size], high);
> > +		add_to_buddy_head(&page[size], zone, high, migratetype);
> >  	}
> >  }
> >  
> > @@ -1877,9 +1896,7 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
> >  							struct page, lru);
> >  		if (!page)
> >  			continue;
> > -		list_del(&page->lru);
> > -		rmv_page_order(page);
> > -		area->nr_free--;
> > +		remove_from_buddy(page, zone, current_order);
> >  		expand(zone, page, order, current_order, area, migratetype);
> >  		set_pcppage_migratetype(page, migratetype);
> >  		return page;
> > @@ -2795,9 +2812,7 @@ int __isolate_free_page(struct page *page, unsigned int order)
> >  	}
> >  
> >  	/* Remove page from free list */
> > -	list_del(&page->lru);
> > -	zone->free_area[order].nr_free--;
> > -	rmv_page_order(page);
> > +	remove_from_buddy(page, zone, order);
> >  
> >  	/*
> >  	 * Set the pageblock if the isolated page is at least half of a
> > @@ -7886,9 +7901,7 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
> >  		pr_info("remove from free list %lx %d %lx\n",
> >  			pfn, 1 << order, end_pfn);
> >  #endif
> > -		list_del(&page->lru);
> > -		rmv_page_order(page);
> > -		zone->free_area[order].nr_free--;
> > +		remove_from_buddy(page, zone, order);
> >  		for (i = 0; i < (1 << order); i++)
> >  			SetPageReserved((page+i));
> >  		pfn += (1 << order);
> > 
>